google/gmail is also one of the principal agents which declares by fiat "your own domain self-run mail is spam because I think its spam" which then propagates to other mail providers.
SPF/DKIM no matter: if they decide it's spammy, un-doing this decision is appeal to a star chamber you cannot interact with directly.
Aside from the sharing of RBL lists, the reflexive bouncing of mails? SMTP error codes rejecting delivery transitively? Maybe I'm wrong and there is no information sharing here? Not impossible or implausible. Does Macys tell Gimbels?
Another effect here is volume. That's non communicating between the big players but would inevitably lead to similar outcomes if they rank domains by volume/score weights.
Hosting a small mail domain in Google is a good way not to get marked bad it seems. Postini filtering on your gsuite user side is an added bonus. I've yet to withdraw a domain from gsuite so I don't know how long it stays "acceptable" But I do know Gmail is one of the principal "not an acceptable sender" paths. As to how that flows or informs o365 or any other player, I may be making a bridge too far.
SPF/DKIM no matter: if they decide it's spammy, un-doing this decision is appeal to a star chamber you cannot interact with directly.